1. Field of the Invention
This invention relates to a coating apparatus having a non-orthogonal coater geometry to improve coatings on a substrate, and more particularly, to position coating nozzles of a chemical vapor deposition (“CVD”) coater relative to the surface of a glass ribbon such that the direction of flow of coating vapors from the coating nozzles and the direction of movement of the glass ribbon subtend an angle measured in either a clockwise or counter-clockwise direction relative to the flow of the coating vapors or the direction of movement of the glass ribbon that is greater than zero degrees and less than ninety degrees.
2. Discussion of the Technology
Environmental coating layers are applied to a glass surface to selectively control the transmission of ultraviolet radiation, visible light, and/or infrared energy through the glass. One of the coating processes for depositing the environmental coating layers is known in the art as chemical vapor deposition (“CVD”) coating process. The CVD coater apparatus in general includes a pair of spaced gas curtain inlet slots or nozzles having one or more coating areas between the gas curtain slots and facilities to exhaust the coating area. Each of the coating areas includes a coating nozzle or slot between a pair of spaced exhaust slots or nozzles. CVD coaters having two or more coating areas usually have an exhaust slot between and distanced from adjacent coating nozzles to provide an exhaust slot on both sides of the coating nozzles. The coating nozzles and exhaust slots each have an elongated shaped outlet opening across the width of the coater.
A continuous glass ribbon moves under the coating nozzles and exhaust slots of the CVD coater as the coating vapors move through the coating nozzles and over the surface of the glass ribbon toward and into the exhaust slots. The coater can be mounted in a glass forming chamber, e.g. but not limiting to the discussion, as taught in U.S. Pat. Nos. 4,853,257 and 5,356,718, in which instance the glass ribbon is moved along a path in a downstream direction toward the exit end of the glass forming chamber, or the coater can be mounted between the exit end of a glass forming chamber and the entrance end of a glass annealing lehr, e.g. but not limiting to the discussion as taught in U.S. Pat. Nos. 4,584,206 and 4,900,110, in which instance the glass ribbon is moved along a path in a downstream direction toward the entrance end of the glass annealing lehr. U.S. Pat. Nos. 4,584,206; 4,853,257; 4,900,110, and 5,356,718 are hereby incorporated by reference.
Although the presently available CVD coaters and coating processes are commercially acceptable, there are limitations. More particularly and as discussed in more detail in the DETAILED DISCUSSION OF THE INVENTION presented below, particles of debris accumulate on the edges of the inlet slot opening of the coating nozzle and/or the edges of the opening of the exhaust slots. The debris reduces the width of the outlet opening of the coating nozzle and/or exhaust slot, which results in a disruption of flow due to the Bernoulli Effect either reducing or accelerating the flow of the coating vapors through the opening of the coating nozzle and/or exhaust slot. This disruption or reduction in the flow of coating vapors results in a coated layer or film having a coating streak. The options available when coating streaks are observed in the coating include, but are not limited to, removing the debris from the outlet opening of the coating nozzle and/or exhaust slot, and/or salvaging the coated glass on each side of the coating streak and discarding the glass with the coating streak.
As is appreciated by those skilled in the art, stopping the coating operation to clean the debris from the opening of the coating nozzle and/or the exhaust slot, and/or discarding glass with the color streaks, are costly expedients to solving the problem. It would be advantageous, therefore, to continue the operation of the coating process while eliminating or minimizing the impact of the debris on the outlet opening of the coating nozzle and/or the exhaust slot on the coating applied to the glass ribbon.